fix creating sub-folders in plugins

plugin_installer/manifest.ini

 [info]
 name: Plugin Installer
 short_name: plugin_installer
-version: 0.12.1
+version: 0.12.2
 description: Install and upgrade plugins from ftp
 authors: Denis Fomin <fominde@gmail.com>
  Yann Leboulanger <asterix@lagaule.org>

plugin_installer/plugin_installer.py

@@ -619,6 +619,7 @@ class Ftp(threading.Thread):
 
             # creating dirs
             for dir_ in dirs:
+                dir_ = dir_.replace(self.plugin.server_folder, 'plugins')
                 try:
                     os.mkdir(os.path.join(local_dir, dir_))
                 except OSError as e: